Charge control resin, and toner

Abstract

A charge control resin containing a copolymer which has a unit having a sulfonic acid ester group having a specific structure and has the unit in specific proportions. The charge control resin can provide a toner with superior charging performance. Also disclosed is a toner having such a charge control resin.

Description

TECHNICAL FIELD[0001]This invention relates to a charge control resin contained in a toner for developing electrostatic latent images in image forming processes such as electrophotography, electrostatic printing and so forth or a toner for forming toner images in an image forming process of a toner jet system. This invention also relates to a toner containing such a charge control resin. More particularly, it relates to a toner used in a fixing system in which toner images are fixed by heat and pressure to a transfer material such as a print sheet.BACKGROUND ART[0002]Conventionally, in image forming processes carried out by electrophotography, electrostatic printing and so forth, the system is so set up that toner particles charged electrostatically develop electrostatic latent images on a photosensitive drum by the aid of an electrostatic force corresponding to potential differences produced on the photosensitive drum. Here, the toner is electrostatically charged by, stated specifi...

AI Technical Summary

Benefits of technology

The present invention provides a charge control resin and a toner with good charging performance and fixing performance. The charge control resin contains a copolymer with specific formulas, and the toner contains the charge control resin and a binder resin, colorant, and other components. The technical effects of the invention are stable developing and transfer performance over a long period of time, resulting in high-quality images.

Problems solved by technology

However, many binder resins used commonly in toners have low triboelectric charge characteristics, and it is not easy to control the charging performance by controlling their composition.

Charge control agents containing these dyes or pigments are structurally complicated, are not constant in properties and have a poor stability.

In particular, almost all of them cause changes in charging performance depending on environmental factors such as temperature and humidity.

Hence, such an additive may come off toner surfaces because of friction between toners themselves, their collision with a carrier, their friction with a transport sleeve or roller, a toner layer thickness control blade and a photosensitive drum to cause contamination of the carrier and so forth and contamination of developing members and the photosensitive drum.

As the result, with an increase in the number of sheets during running, the charging performance becomes poor and at the same time any deterioration due to contamination also becomes worse to cause problems such as changes in image density and a lowering of image quality.

As stated above, charge control agents capable of imparting a sufficient charging performance to toners stably over a long period of time are seen to be very limited.

Therefore, taking account of these, only very few agents are feasible for practical use.

In these toners, however, glass transition point of toner and melt viscosity of toner may lower as the wax blends with the binder resin, and hence, besides storage stability and fluidity, the charging performance tends to be damaged when it is aimed to further improve the low-temperature fixing performance, to tend to cause a great decrease in density and image defects especially when printed continuously.

This is because, as the toner merely has a small particle diameter, the toner particles adhere to the photosensitive member at a larger force (image force or van der Waals force) than Coulomb force acting on toner particles in the step of transfer, and, in addition thereto, since making toners have smaller particle diameter concurrently makes the toner have poor fluidity, the toner particles tend to have non-uniform charge quantity, so that toner particles causative of fog and having poor transfer performance may come present in a large number.

However, as a result of studies made by the present inventors on these toners, it has turned out that they have a problem that, when printed on a large number of sheets, a toner charged to a reverse polarity increases gradually in a developing assembly to make what is called reversal fog rapidly come to occur seriously.

Also, in these publications, disclosed is only a binary copolymer composed of styrene and 2-acrylamido-2-methylpropane sulfonic acid, and the binary copolymer disclosed therein has a glass transfer material temperature of 90° C. or more, and has caused a problem on the low-temperature fixing performance in some cases.

However, in these publications as well, the achievement of both charging performance (in particular, rise performance at the initial stage) and fixing performance can not be well satisfactory.

In regard to the charging performance, however, there is further room for improvement, and also these toners can not be said to be sufficient in regard to the low-temperature fixing performance as well.

Further, in the toners disclosed in these publications, their transfer performance is not sufficient to cause problems on image quality in some cases.

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